Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Rabin code same message sent with different $N$

I use Rabin code with modulus $N$. Now assume that Alice sends me a message $m$ $(1\le m\le N)$ encoded by Rabin code. Unfortunately after Alice sent me the text I lose the information about the ...
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122 views

One-time pad mistake in the transmission?

I have a question which arised by analyzing the one-time pad cipher. I encrypt a binary sequence $a_1,a_2,..,a_N$ using a one-time pad with key sequence $k_1,k_2,k_3,...$, so I send $a_1+k_1, ...
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Low Public Exponent Attack for RSA

I'm having trouble understanding the algorithm for finding the original message $m$, when there is a small public exponent. Here is the example I'm trying to follow (you can also read it in the 'Low ...
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346 views

RSA cipher wrong use

Why is it foolish if you decide to use an RSA cipher to encode some message by first converting each letter of the message to an integer? So for exmaple Space=0, a=1, b=2,... After the conversion I ...
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812 views

Java's SecureRandom & plaintext attack?

Java's SecureRandom is meant to be cryptographically secure, and I know part of that means that the output should not be usable to predict further output. Though, ...
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648 views

Json AES128: Security against known plaintext attack

I have a system where I am transmitting json messages securely (using for example AES-128), where each message has the same format. For example ...
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1answer
710 views

What is the theoretical and practical status of mental poker?

I'm able to find a lot of scattered papers on the development of mental poker since RSA proposed the initial solution but no recent report (i.e. after 2005) on what is the status of the problem, eg: ...
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200 views

EC equivalent for RSA-OAEP

I have some questions regarding aforementioned subject: Is there a EC equivalent of RSA-OAEP key transport/encryption algorithm ? Is ECIES-KEM sufficient ?
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FIPS 140-2 compliant algorithms in Enhanced RSA and AES Cryptographic Provider (Windows XP) [closed]

We have a native C++ application that supports Windows XP SP3. Recently we've decided to change our crypto algorithms to FIPS 140-2 compliant ones. We are planning to use the following algorithms in ...
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AES Algorithm processing time in Arduino vs Raspberry Pi

The Arduino employs an 8-bit ATmega series microcontroller whereas the Raspberry Pi is based around a 32-bit ARM processor, and the Arduino is typically clocked at between 8-16MHz and with 2-8kB of ...
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376 views

Is it possible to decrypt double-key crypted file knowing public key and a having one or more original files?

I have some encrypted files with double-key. I know public key and don't know private key. Can I obtain the private key (and decrypt all files) using two version of one file - crypted and decrypted? ...
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321 views

Brute force a ciphered message? [closed]

I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
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Can you show how that RSA does/doesn't provide anonymity?

Considering a CPA-secure version of RSA where the ciphertext is just a rundom element from $Z^*_N$. Does that meet the anonymity requirement in which an cpa adversary cannot distinguish between a ...
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Why RSA encryption key is based on modulo $\varphi(n)$ rather than modulo $n$

While calculating RSA encryption key we take modulo $\varphi(n)$ rather that modulo $n$. I couldn't understand why its so?
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2answers
236 views

How can A pass a message to B, while preventing a third party from sniffing infos?

$A$ has a message that he wants to send to $B$, without a third party being able to learn the contents of the original message. $A$ encrypts the message and sends it to a server. The server decrypts ...
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1answer
117 views

is there an algorithm to encrypt all the datatypes?

Is there an algorithm or technique to encrypt all the datatypes such as (video , image , text , fax, audio ,file,etc...) -one algorithm encrypt every thing-? also if I try to build such this ...
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632 views

How does Clifford Cocks 'Non-Secret Encryption' work?

I have read Clifford Cocks "A Note on 'Non-secret Encryption'" and thought I would try to implement this, but I don't seem to be able to get it to work. I'm obviously missing something. From the ...
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3answers
534 views

How to submit a new method of encryption?

I came up with a truly new method of applying modulo-2-addition encryption function in stream ciphers which is inspired by a mechanism used to prove a mathematical theorem. How can I determine whether ...
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1answer
246 views

Storing the activation status of a product and expire details Android [closed]

In my Android application, it's required to store the activation status of the software and keep track of the activation expire date. What is the best way to store this information? Is it safe to ...
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1answer
70 views

function of crypt called “ICE” [closed]

Using exeinfo, I have identified a function of crypt called ICE. What is it? How can I find ...
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1answer
871 views

Is it possible to crack a blowfish 256 bits encrypted file? [closed]

I have a file of my own that I have encrypted using Coder-Abi. Now, I can just remember part of this password. So, would it be possible (much easier) for me to crack it knowing only part of it? I can ...
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1answer
251 views

Can you help me understand hash-preserving encryption?

I have rather simplistic understanding of cryptography, so I have to beg a pardon in advance if the question has internal contradictions. Imagine data $A$ with a hash $hashA$. This data is encrypted ...
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What characters does AES output?

From what I understand after testing the Crypto-JS file here: http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js AES creates encrypted strings that contained letters, both ...
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1answer
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Removing Padded Value in Decrypted Message

How to remove padded value in Decrypted Message? I am using AES Algorithm. Let's take this as the decrypted message: "abcdefghijklmn " There is a 2 space in ...
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1answer
2k views

Why does OpenSSL append extra bytes when encrypting with aes-128-ecb?

Plaintext: Attack at dawn!! Hex: 41747461636b206174206461776e2121 Key: ...
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211 views

Solve a Modular Exponentiation

It might be common, but if we had to solve an equation like this $m=s^{e}$ mod $n$ where $m,e,n$ are known. How can we find $s$. What optimisations could be applied? And what would the complexity of ...
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1answer
128 views

With Encrypt-then-MAC, and flexible protocols, do I need to authenticate the authentication?

Sorry, the question is not easy to state (or wasn't for me, anyhow). So I'm writing a very flexible format for security. It allows for full choice of cipher, key size, and so on, along with key ...
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409 views

Guessing encryption algorithm based on key and ciphertext

Is it possible to tell which encryption algorithm was used, assuming I have a key and a encrypted text? To not complicate the situation let assume we are speaking about symmetric algorithms only. ...
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1answer
159 views

In S/MIME, are the same certificates always used to sign and encrypt messages?

My assumption is that S/MIME almost always utilizes certificates as follows: My certificate can be used to allow people to encrypt messages and send them to me. My certificate (the same ...
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1answer
105 views

Diffie-Hellman for Encryption

In learning how DH works for cryptography applications, I'm coming across some confusing language. For starters, most of the time DH is discussed in the context of "generating" their shared secret. ...
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465 views

AES column mixing and S-Box confusion

I am trying to understand the AES encryption algorithm. I know that we process 128 bits at a time for a 128 bit key in a 4x4 octet form, but am confused by the following: How does the substitution ...
3
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2answers
903 views

Determine the Key given ciphertexts and plaintexts?

Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$? The ciphertexts are: $$C_1= (P_1 \oplus K_0) + K_1$$ and $$C_2= (P_2 \oplus K_0) + K_1$$ $K = ...
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281 views

Diffie-Hellman: Does the size of the prime modulus depend on the potential size of the secret?

I'm writing my own cryptosystem that uses One Time Pad and Diffie-Hellman to generate keys for the OTP. I am using Rails on the server side and Javascript for the client side. Please don't tell me ...
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71 views

PRP representation size

I'm now studying the block cipher substitution-permutation network construction and realized that it uses several small pseudo-random permutations instead a big one for saving memory (or that is one ...
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189 views

Can you help me with this DES variant analysis?

I'm struggling with some DES variant that I got as an exercise (exercise taken from Katz-Lindell Ex5.14). The variant is as follows: The left half of the master key is used to derive all the ...
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Why are these techniques not feasible to crack RSA?

For $d = e^{-1} \mod \phi(n)$ $$d\cdot e \operatorname{mod} \phi(n)=1$$ $$d = (e^{-1} \operatorname{mod} \phi(n))$$ With having $e$ and $n$, we can calculate the value of $d$ , the private key for ...
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Increasing the diffusion of the AES-CBC encryption algorithm in pycrypto for python

When encryption is done using the AES-CBC algorithm, the encryption can be thought of as chaining the cipher texts with the previous ones and an IV. However, if its on CBC mode, we give our cipher ...
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1answer
126 views

How do we arrive to the equation for solving D in RSA?

We have been shown that DE is congruent to 1 mod phi(n). How do we arrive to the real equation for figuring out d that is d = e^-1 mod phi(n). I want to know the entire process. I am just curious, ...
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Using the same RSA keypair to sign and encrypt

The RSA signature operation is basically the same as encrypting with the private key. In particular, both operations use the same kind of keys. Is it safe to use the same RSA keypair both for ...
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1answer
265 views

XOR cipher Pseudo-random key strength

When implementing a XOR cipher with a pseudo-random key equal in length to the plaintext, Is there a significant difference in potential key strength between keys drawn from a pool of either 1000 or ...
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Ciphers in CBC mode reveal place of change in plaintext

Theoretically, when using a symmetric block cipher in CBC mode, the current block is dependent on the previous block. Suppose one plaintext is encrypted using CBC, and then one bit of it is changed, ...
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Shamir's Simple Sharing Scheme - preventing partial recovery of data

In SSSS, if you recreate the original secret with one of the decoder inputs being slightly damaged (e.g. one or two chars incorrect), you receive a slightly damaged version of the original secret. So ...
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Is the following symmetric design secure?

Assume: $O$ be a reversible random permutation oracle on a finite set and $O^{-1}$ the inverse permutation (pretty much equivalent to a random permutation: What is the difference between a bijective ...
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Is CBC really dead?

I developed a p2p-app in C# which sends and receives encrypted text messages (50KB). For encryption, my app uses AES 128 bit in CBC cipher mode. For each message it uses a new randomly-generated IV. ...
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2answers
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How to obtain KCV from the key

Simple question: we have AES 128 encryption and a key. How can we calculate the key check value (KCV)? One example: key is 48C3B4286FF421A4A328E68AD9E542A4 and KCV should be 77DC84. I am trying it ...
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3answers
162 views

Help me about Advanced Encryption Standard (AES)

Suppose $E_k$$(a, b, c)$ is encryption of values $a, b$ and $c$ with key $k$ through encryption algorithm AES (AES-128) and each $a, b$ and $c$ are 300 bits integer values. Also Suppose this ...
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What scheme will allow merging and splitting the result of a function?

I am wondering if it's possible to have a scheme as follows. Here is the scenario: we have a set of objects (e.g. strings) {O1, O2, ..., On} we have a set of users {U1, U2, ..., Um} each user asks ...
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AES and Known-plaintext attack [duplicate]

Can you help me to finding some papers that shows AES is secure against known-plaintext attack?
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100 views

Creating a secure key

Imagine that your lecturer and the undergraduate office have conducted a key exchange protocol after which both of them hold the string $X$. Yet, it is possible that a curious student sitting next to ...
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145 views

Encoding multiple fields with same AES key and vector?

I'd like some advice on cryptography best practices. I need to store on my web app the users' credentials (login & password) for 3rd-party sites. I'm using AES-256 with random key and ...